[Demonstration of increased natural spontaneous activity of cranioesophageal and laryngeal muscles by PET-CT].

The muscles of the cranioesophageal sphincter system feature continuous natural spontaneous resting activity. Thus, they resemble the anorectal sphincter system. We studied metabolic activity and morphology of the proximal sphincter system at rest in 23 individuals (14 females, nine males) using PET-CT scanning. We found that metabolic activity was significantly higher than in other muscle groups of the body at rest (P=0.001). In contrast to the horizontally oriented anal sphincters, the proximal sphincter system is developed as a vertical assembly of long, interlocking muscular tubes. These are innervated by five cranial nerves and three sensory organ nerves and form a functional unit that extends from the orbicularis oris muscle via the pharynx and larynx to the lower esophageal sphincter. The larynx shows only one active muscle, i.e., the posterior cricoarytaenoid muscle, that maintains airway patency. The lower esophageal sphincter can be visualized by PET-CT as a vertically oriented stretching sphincter. It features a spiral-shaped design made up of muscle maxima and minima which correlates well with its asymmetric muscle activity. This complex proximal sphincter system shows great developmental variability among different animal species. However, the general functional principle is similar in all.